Propylene polymers and propylene-α-olefin copolymers are used in broad fields, because they are inexpensive and have superior properties such as mechanical property, heat resistance, solvent resistance and water resistance. However, such propylene polymers generally have low polarity because of the absence of polar groups in their molecules, thus posing a disadvantage of being difficult to effect coating and adhesion. In order to improve this disadvantage, various techniques have been attempted, such as chemical treatment of the surface of moldings of these propylene polymers with solvents and oxidation treatment of the surface of moldings by techniques such as corona discharge treatment, plasma treatment and flame treatment. However, these methods require special apparatus, and it cannot be said that their effects to improve coating property and adhesiveness are sufficient.
Accordingly, a so-called chlorinated polypropylene has been developed as a device for adding good coating ability and adhesiveness to propylene polymers by a relatively convenient method. The chlorinated polypropylene is generally soluble in hydrocarbon solvents such as toluene and xylene and, what is more, its adhesiveness to base materials such as propylene polymers is relatively good. Thus, coating ability and adhesiveness of propylene polymers can be improved by a relatively simple method in which a hydrocarbon solution of the chlorinated polypropylene is coated on the surface of a propylene polymer to be used as the base material and then the solvent is removed. In this connection, it is known that a modified chlorinated polypropylene obtained by further modifying the chlorinated polypropylene by graft copolymerization of a polar monomer has further superior effect to improve coating ability and adhesiveness.
Accordingly, though coating ability and adhesiveness of propylene polymers can be improved relatively conveniently using the chlorinated polypropylene or modified chlorinated polypropylene, there is a problem of containing chlorine in a large amount. In recent years, the use of vinyl chloride resins is causing a social problem due to possible generation of toxic substances by inadequate incineration of the resins, and the chlorine-containing resins also have problems remained unsolved such as poor weather resistance. Thus, great concern has been directed toward the development of a substitute resin for chlorinated polypropylene as in the case of vinyl chloride resins, which does not contain halogens such as chlorine.
In view of such background, on the other hand, development of a resin containing no chlorine has been attempted. For example, Japanese Patent Publication No. 958/1969 discloses a treating agent in which an amorphous polypropylene polymer modified with a specified ratio of maleic acid or its anhydride is dissolved in a solvent. In this case, the amorphous polypropylene polymer is an amorphous polymer which contains at least about 20 mol % of propylene unit in atactic polypropylene and copolymer as occasion demands and comprises a copolymer of at least one comonomer and propylene. Also, as a similar treating agent, Japanese Patent Laid-Open No. 217835/1996 discloses an amorphous polymer in which unsaturated carboxylic acids having from 3 to 10 carbon atoms are graft-copolymerized with an amorphous polypropylene or amorphous propylene-1-butene copolymer. When such a graft modified polymer is used, it has improved solubility and superior coating ability in comparison with general modified propylene resins, but it still has low solubility in solvents at room temperature, shows stickiness, and is poor in adhesiveness. Thus, for the purpose of using as a finishing agent, an adhesive or a paint, it is considered that the chlorinated polypropylene or modified chlorinated polypropylene is a relatively excellent resin at present.